Concentration of phosphate ores



April 27, 1954 J. B. DUKE ETAL CONCENTRATION OF PHOSPHATE ORES Filed Dec. 27, 1951 I; Phosphate Ore Feed Coarse Fraction of Phosphate Ore Feed Fine Fraction of Phosphate 0re Feed Negative-Mn Peagents,such as caustic soda, t'attyacidand fuel oil Conditioning Cond/tining Coarse Concentrating Method Pougher F latation Si/iciaus Machine Discharge J to Waste Coarse Pougher Phosphate Concentrate I Froth-Products, containing entrained sand particles Pougher Phosphate Concentrate cidu/ated Water Petarde d Flo t a tion Phosphate-rich Machine Fine Phosphate Canpischarge centrate FrothProduct Mineral Acia', such Sulfuric Acid Agitation Water Pinsing Spent Reagents, V .Sli/nes and Water to Waste Acid TreatedProduc/s Posit/ve'ion Reagents such as the higher aliphatic aminesetc. flotation .Si/icious Frothi l I i Mach/ne-D/scharge, Prom/ct to Waste Phosphate Concentrate Final Highrade Concentrate of both coarse and fine Phosphate IN VEN TORS JAMES B. DUKE BY WESLEY/M HOUSTON A ttorneys Patented Apr. 27, 1954 James B. Duke, Medull Lakeland, Fla

erals & Chemicals Cor of Maryland a, and Wesley Houston, assignors to Attapulgus Minporation, a corporation "Application December 27, 1951, Serial No. 263,546

1 Claim. '1

The present invention relates to the concentration of phosphate minerals from their ores,

andmay be regarded as an improvement .upon the ,method described in our co-pending :application, Serial No; 177,374, which is assigned'to the assignee of the present application.

Thegeneral object of the present invention is totobtain from a phosphate ore, containing ore particles which are too coarse vfor froth-flotation treatment (as well as particles which are fine enough .tor froth-flotation treatment, a final high-grade concentrate containing a i-h-ighi per centage of both thecoarse and fine phosphate particles; and to achievethis result with econ- ,omyuin the-reagents employed, particularly the positive-ion reagents which are expensive. To this end, the. invention involves separate "appropriate treatments with the use of negativeion reagents of the 'coarseaand fine .fractions ,of the phosphate ore, followed by de-oiling and then by froth-flotation treatment with the use of positive-ion reagents of a mixture of the products resulting from said initial treatments. Some of the advantages of the invention are economy in the positive-ion reagents employed, and the production of a final high grade phosphate concentrate containing bothcoarse and fine particles from the whole of the phosphate ore, andra considerable increase in the usual recovery of the phosphate particularly in the coarse fraction of the ore. The manner in which these advantages are achieved will be understood from the following description of methods embodying the invention.

The invention will be understood from the following description, taken in connection with the accompanying drawing which is asimplified-general flow-sheet of a typical plant practicing the invention. It will be understood that this "flowsheet merely contributes to an understanding of the invention, and that various modifications in' the methods used and the apparatus employed may be resorted to without departing from the spirit of the invention as defined in the claims hereto appended.

The operations represented in the flow-sheet will now be described. The phosphate ore feed is divided into coarse .and finefractions.

As indicated at the upper left part of the flowsheet, the coarse fraction of the phosphate ore feed is treated with negative-ion reagents such as caustic soda, fatty acid and fuel oil, and is then subjected to a separating treatment, .(including, if advantageous, a cleaning retreatment of the concentrate) resulting in a siliceous machine-discharge (which is sent to waste) and a v:coarse :rougher phosphate concentrate containing entrained sand particles. This separating treatment may be carried out in any suitable apparatus, such as .belt separators such as are described .in II. .S. patents to .Greene and Wilbur,.l\Tos.i2,047,773..and2,231,066; or helical separatorssuch as are described in II. S. patents to .Humphreys Nos. 2,431,559 and 2,431,560,; or shaking tables which are customarily used for the concentratingtreatment of a phosphate ore having particles too largetopermit the ore to lbeadvantageously treated in froth -flo.tation .cells. This operation produces from the coarse free-- tion of the feed a coarse rougher phosphate concentrate containing the finer entrained sand particles; and a siliceous machine discharge, 'containingmostof the coarsersiliceous particles, which .issent to waste. It will :be understood that thiscoarse phosphate rougher concentrate may be submitted to .a cleaning. operation if idesirable.

As shown ,at the-upper right-hand portion of the flow-sheet, :thefine fraction of the phosphate .ore ,feedis also conditioned with negative-ion reagents, such as those which have been mentionedpandis then subjected to flotation treatment flotation cells .of any-welltknown kind. This flotation treatment results in a froth-prodnot which Lisa rougher phosphate concentrate, and a siliceous machine discharge which is sent to waste. This rougher phosphate concentrate is then subjected to retarded-flotation treatment, bylwhich is meant ,-a treatment which restrains the normal. .floatabilityr of the phosphate and produces a fine phosphate concentrate frothproductlofisuch high grade that it is treated as a pastor 'thefinalphosphate concentrate; the machine discharge from the retarded flotation treatment .beinga phosphate-rich product. This retardedefiotation treatment may be carried out in several ways, as explained in our prior icopending application above mentioned. As represented in-the flow-sheet, the retarded-flotation treatmentismade possible by the fact that to the rougheriphosphate concentrate which is the teed 'to thatftreatmen't is addedacidulated water having a lowpI-I, say about -3. However, as pointedjout .in our priorlapplication, instead of using .acidu'lated flotation water having a low pH, it is possible to obtain retarded-flotation by subjecting the feed to that operation to agitation and scrubbing withordinary (neutral) ,fiotation water; oryretarded-flotation may be accomplished merely by maintaining the level of the pulp in the flotation cells so low that only the top portion of the Iroth product is removed.

.As'illustra'ted in the lower half of the flowsheet, the coarse rougher phosphate concentrate containing entrained sand particles, obtained fromthe coarse fraction of the feed, is combined withthe phosphate=rich residue obtained from the retarded-flotation treatment of the rougher phosphate concentrate from the fine fraction of the feed. This mixture is the feed to the operations which will now be described. In order to remove the effect of the negative-ion agents, this feed is treated with a mineral acid and rinsed. (As in the method of the patent to Arthur Crago 2,293,640 issued August 18, 1942, now owned by the assignee of the present application.) shown in the flow-sheet this acid-treated material is conditioned with positive-ion reagents, such as the higher aliphatic amines, etc. and is then subjected to froth-flotaton treatment in flotation cells which results in a siliceous froth-product which is removed and sent to waste, and a machine discharge which is a high-grade phosphate concentrate, which is combined with the highgrade phosphate concentrate which was the froth-product from the retarded-flotation treatment. Thus, from the original phosphate ore, is produced a final high-grade phosphate concentrate containing a high proportion of both the coarse and the fine phosphate particles in the original ore.

The method which is the present invention will be understood from the foregoing description, but an example of the practicing of the invention will now be described in order to show the advantages thereof.

Example A deslimed phosphate ore feed was classified into two size fractions: a coarse fraction which was substantially 14+65 mesh and represented 25% by weight of the original feed; and a fine fraction which was substantially -35 mesh and represented 75% by weight of the original feed.

The coarse fraction of the deslimed phosphate ore feed was conditioned in an aqueous pulp for 2 minutes at 70% solids with negative-ion reagents consisting of 0.4 pound of caustic soda, 4.5 pounds of fuel oil, and 0.? pound of tall oil, all in pounds per ton of the dry coarse fraction of the feed. This conditioned feed was then treated in a minerals separation laboratory belt separator apparatus in the usual way, thereby producing a coarse rougher phosphate concentrate, and a sand tailing which was discarded. This rougher concentrate was returned to the belt separator for re-treatment, without the addition of reagents, and was subjected to a cleaning separation, thereby producing a phosphate-sand middling product which was sent to waste but might have been recirculated to the feed; and a coarse rougher phosphate concentrate containing entrained sand particles which was retained for the further treatment hereafter described.

The finer fraction of the deslimed phosphate ore feed was conditioned in an aqueous pulp for 2 minutes at 70% solids with negative-ion reagents consisting of 0.4 pound of caustic soda, 3 pounds of fuel oil, and 0.25 pound of tall oil, all in pounds per ton of the dry fine fraction of the feed. This conditioned feed was diluted with tap water to about 20% solids in a minerals separation laboratory airflow fiotation machine, agitated and aerated to produce a sand tailing in the machinedischarge which was discarded; and a froth-product which was a rougher phosphate concentrate.

This rougher phosphate concentrate was dewatered and repulped in the flotation machine at about solids with water to which suflicient sulfuric acid had been added to produce a pH of 3, employing for that purpose approximately 1.8 pounds of H2504. per ton of the fine fraction of the feed. The rougher concentrate was agitated briefly and then aerated and refloated in this acid pulp, thereby producing a retarded-flotation of a high-grade final phosphate concentrate containing a minimum sand content; and a phosphaterich machine-discharge consisting of both phosphate and sand particles.

The coarse rougher phosphate concentrate containing entrained sand particles, obtained from the belt separator, was then combined with the phosphate-rich residue obtained from the retarded-flotation step. This mixture was agitated for 3 minutes at approximately 50% solids with 4.0 pounds of sulfuric acid per dry ton of said mixture, and was then washed and rinsed substantially free of acid and spent negative-ion reagents. This acid-treated and rinsed mixture was repulped in a flotation cell, conditioned for about 15 seconds with positive-ion reagents consisting of 0.36 pound of Armac T (a tallow amine acetate made by Armour & Company), 0.4 pound of kerosene and 0.23 pound of pine oil frother, all in pounds per ton of the mixture Which was the feed to this operation, and then was aerated and a low-grade siliceous froth-prod not was removed and sent to waste, leaving a high-grade final phosphate concentrate in the machine discharge, which was combined with the finer high-grade final phosphate concentrate obtained from the retarded-flotation step; thereby producing from the original ore a final highgrade phosphate concentrate containing a high proportion of both the coarse and fine particles in the original ore.

The metallurgical results of the above described operations, and the quantities of reagents employed, are recorded in the following tables:

Per- Per- PerfifJ-f Products ce nt cent cent Dis; ll t. BPL Insol bum) Total Feed 100. O 40. 5 100. U Belt Separation (Coarse Fraction of Ore):

1. Feed 25.0 47.1 20. l 2. Bolt Ooucen 1 15.0 76.9 5.6 28. 5 3. Siliceous Talling to Waste. 1 l0. 0 2. 6 0. 6 Rougher Phosphate Flotation,

(Fine fraction of Ore):

4. Feed... 75.0 38.2 70.0 5. Rougher Cone.

Product 37. 0 71. 5 07. 3 6. Siliceous Machine Di to Waste 38. 0 3. 8 5 Retarded Phosphate Flotation:

7. Phosphate Conc. Froth- Product 25. 4 79. 7 2. 7 50. 0 8. Phosphate-rich Machine isc 11.6 60.2 17.3 Sand Flotation from Belt Cleaner Concentrate and Cell Middling (items 2 and 8):

0. Siliceous Froth-product to l a e 4.0 13.7 1.4 10. Machine Discharge, Phosphate Gone 22.0 79.3 2. 6 44. 4 Overall Results:

Total Phosphate Cone. (items 7 and 10) 48. 0 79. 5 2. 7 94. 4 Total Telling (items 3, 6

and 9) 52.0 4.3 5.6

1 Includes circulating middling 5.3% by Weight and 35.4% BPL.

The excellent results and the economy in reagents employed in the example are obvious from the above tables. The overall recovery of the phosphate values from this feed was excellent, being 94.4% of the total fine and coarse phosphate in the feed. Particularly noteworthy was the recovery of BPL values from the coarse fraction of the ore, represented in the belt concentrate, item No. 2 in the table. This high recovery amounted to (28.5 100)/29.1 or 97.9% and is largely attributed to the fact that a maximum grade belt concentrate is not required in this proc ess. Along with these excellent recoiveries, a maximum grade of 79.5% BPL was obtained in the final combined concentrate which contained only 2.7% insoluble.

There are several reasons why the method, as described and illustrated in the example results in a very high recovery of a high-grade phosphate concentrate above mentioned. One reason is that the phosphate particles in the rougher phosphate concentrate (resulting from the initial treatment of the coarse fraction of the ore feed) are so coarse that they have little tendency to float with the silica in the final froth-flotation treatment with positive-ion reagents. Another reason is that the phosphate-rich machine discharge (resulting from the initial treatment of the fine fraction of the ore feed) has been very largely freed of very fine phosphate particles which if present might float with the silica in the final froth-flotation treatment with positive-ion reagents. Therefore, the mixture which is subjected to de-oiling and then to froth-flotation treatment with positive-ion reagents is particularly well suited to that treatment.

The economy achieved in the quantity of expensive positive-ion reagents employed is largely due to the reduction of the weight of the material which is subjected to froth-flotation treatment with those reagents. It will be noted from the example that the weight of the material mixture subjected to de-oiling and. then to froth-flotation treatment with positive-ion reagents was only 26.6% of the weight of the original phosphate feed. In the tabulation, see percent weight in items 3 and 8.

What is claimed is:

The method of jointly concentrating both irougherl; concentrate in an aqueous pulp to agitation fand froth-flotation treatment, thereby producing a fine phosphate froth-product of high-grade which is a part of the final concentrate and a fine phosphate-rich machine-dischagge; mixing said fine phosphate-rich machine-discharge and said coarse rougher phosphate concentrate and subjecting that mixture to treatment with a mineral acid, followed by rin's'ing with water, thereby removing from said mixture substantially all of said negative-ion reagents; and subjecting said acid-treated mixture to a concentrating operation in an aqueous pulp with positive-ion reagents, thereby producing a siliceous froth-product which is sent to waste, and a residue which is a high-grade phosphate concentrate which is the other part of the final concentrate; thereby producing a final highgrade concentrate containing a high proportion 01? both the coarse and fine phosphate particles in the original ore feed.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,480,884 Dolbear Jan. 15, 1924 2,293,640 Crago Aug. 18, 1942 2,350,943 Thompson June 6, 1944 Duke Feb. 15, 1949 I OTHER REFERENCES 

